JP5701508B2 - Conductive resin foam - Google Patents

Description

  The present invention relates to a conductive resin foam that is flexible and has a high expansion ratio. More specifically, the present invention relates to a conductive resin foam having both functions of a conductive material and a buffer seal material.

  Conventionally, in electronic devices such as mobile phones, conductive materials have been used for the purpose of grounding and electromagnetic field shielding from the viewpoint of preventing malfunction of the device. Conventionally, a buffer sealing material has been used for electronic devices such as mobile phones for the purpose of preventing buffering between electronic components and preventing dust from entering.

  However, in recent years, along with the downsizing of electronic devices such as mobile phones, there is a tendency for the number of members mounted inside to be reduced and for electronic components to be mounted at high density. Therefore, a member having both functions of a conductive material and a buffer seal material is required instead of using a conductive material and a buffer seal material separately as in the prior art. Furthermore, a flexible conductive material and a buffer seal material are required so as to fill a minute clearance between electronic components mounted at high density. Further, even in applications where conductivity performance is not required, since the buffer seal material cannot avoid contact with electronic components, it is necessary to prevent the buffer seal material itself from being charged and to prevent static electricity.

  As such a conductive material or a buffer seal material, a conductive material is laminated on the surface of a foam (see Patent Document 1, Patent Document 2, and Patent Document 3), and a conductive cloth is wound around the foam (see Patent Document 4). ), And a foam (see Patent Document 5 and Patent Document 6) in which a conductive material is internally added.

  However, when the conductive material is laminated on the foam surface, the flexibility of the foam is impaired by the conductive material, and in addition, it is difficult to obtain conductivity in the thickness direction (volume resistivity in the thickness direction). .

  Moreover, in the body winding of the conductive cloth around the foam, the flexibility of the foam is impaired by the conductive cloth, and the shape processing by the punching process becomes difficult. In many cases, it cannot be performed, and it has been difficult to obtain a conductive material or a buffer seal material having a sufficient function.

  Furthermore, the foams (Patent Document 5 and Patent Document 6) into which the conductive materials proposed so far are internally added are poor in flexibility due to the low expansion ratio, and the cell diameter is also large. It was difficult and it was difficult to fill a minute clearance between high-density electronic components. Inability to fill the minute clearances between the densified electronic components may cause an increase in the resistance value of, for example, a static elimination (ground) location.

International Publication No. 2002/036667 JP 62-241929 A Japanese Patent Publication No. 4-26615 Japanese Patent Laid-Open No. 11-346082 JP 2006-63249 A JP 2004-83804 A

Therefore, the object of the present invention is excellent in flexibility and conductivity, and it is possible to fill a minute clearance between highly densified electronic components. An object of the present invention is to provide a resin foam that has excellent followability and has a low volume resistivity and can be used as a conductive buffer sealing material.
Another object of the present invention is to provide a resin foam excellent in shape workability in addition to the above-mentioned characteristics. Furthermore, another object of the present invention is to provide a resin foam which is excellent in dustproof property and can be used as a conductive dustproof material in addition to the above characteristics.

  As a result of intensive studies to solve the above problems, the present inventors have determined that, in the resin foam, the volume resistivity is set to a specific value or less and the repulsive load at 50% compression is set to a specific value or less. Combined with flexibility and conductivity, it is possible to fill a minute clearance between high-density electronic components, and can follow the step in the step portion even when compressed, and has a low volume resistivity, Has been found to be suitable for use as a conductive buffer sealing material, and the present invention has been completed.

That is, the present invention is a volume resistivity of less 7.6 × 10 ⁵ Ω · cm, and Ri der repulsive load at 50% compression is 5N / cm ² or less, an apparent density of 0.01 to 0. A resin foam characterized by having an average cell diameter of 10 to 250 μm and a density of 15 g / cm ³ is provided.

Furthermore, the present invention provides the resin foam, wherein the resin foam has a surface resistivity of 10 ¹⁰ Ω / □ or less.

  Furthermore, this invention provides the said resin foam whose expansion ratio of a resin foam is 9 times or more.

  Furthermore, this invention provides the said resin foam formed from the resin composition containing resin and an electroconductive substance.

  Furthermore, this invention provides the said resin foam whose electroconductive substance is a carbon-type filler.

Furthermore, this invention provides the said resin foam whose resin is a thermoplastic resin.

Furthermore, the present invention includes a thermoplastic resin and a carbon-based filler, wherein the carbon-based filler has a BET specific surface area of 500 m ² / g or more, and the added amount of the carbon-based filler is 3 to 100 parts by weight of the thermoplastic resin. The resin foam is provided in an amount of 20 parts by weight, an average cell diameter of 10 to 250 μm, and an apparent density of 0.01 to 0.15 g / cm ³ .

  Furthermore, this invention provides the said resin foam which has a closed cell structure or a semi-continuous semi-closed cell structure in a resin foam.

  Furthermore, this invention provides the said resin foam formed through the process of pressure-reducing, after impregnating the resin composition containing resin and an electroconductive substance with a high pressure inert gas.

Furthermore, the present invention includes a thermoplastic resin and a carbon-based filler, wherein the carbon-based filler has a BET specific surface area of 500 m ² / g or more, and the added amount of the carbon-based filler is 3 to 100 parts by weight of the thermoplastic resin. The resin foam is formed by impregnating a resin composition of 20 parts by weight with a high-pressure inert gas and then reducing the pressure.

  Furthermore, this invention provides the said resin foam whose inert gas is a carbon dioxide.

Furthermore, the present invention provides the above resin foam in which the inert gas is in a supercritical state.
Furthermore, this invention provides the said resin foam used as a buffer sealing material.

  Furthermore, the present invention provides a conductive foam member having an adhesive layer on one or both sides of the resin foam.

  Furthermore, this invention provides the said electroconductive foaming member by which the adhesion layer is formed on the foam through the film layer.

Furthermore, this invention provides the said electroconductive foam member in which the adhesion layer is formed with the acrylic adhesive.
Furthermore, this invention provides the said electroconductive foam member used as a buffer sealing material.

  According to the resin foam of the present invention, since it has the above-described configuration, it has both flexibility and conductivity, and can fill a minute clearance between highly densified electronic components. Even when compressed, the step portion can follow the step and has a low volume resistivity and can be used as a conductive buffer sealing material.

It is a schematic sectional drawing which shows the evaluation method of clearance followable | trackability. It is a schematic block diagram which shows an example of a dustproof evaluation test apparatus. It is a schematic structure sectional view showing an example of a dustproof evaluation test device. It is a schematic sectional drawing of the upper electrode which affixed PET tape.

The resin foam of the present invention has a volume resistivity of 10 ¹⁰ Ω · cm or less and a repulsive load at 50% compression of 5 N / cm ² or less. The resin foam of the present invention is usually formed from a resin composition containing a resin and a conductive substance.

(Resin foam)
The resin foam of the present invention has a volume resistivity of 10 ¹⁰ Ω · cm or less and a repulsive load when compressed to 50% of the initial thickness (a repulsive load at 50% compression, 50% compressive load). ) Is 5 N / cm ² or less. Thus, the resin foam of the present invention is excellent in conductivity and flexibility, and is applied to conductive materials, shock absorbing materials, buffer seal materials, conductive buffer seal materials, dustproof materials, conductive dustproof materials, and the like. Is possible. The resin foam of the present invention preferably has a sheet shape or a film shape.

The volume resistivity of the resin foam is 10 ¹⁰ Ω · cm or less, preferably 10 ⁸ Ω · cm or less, and more preferably 10 ⁵ Ω · cm or less. The volume resistivity of the resin foam is measured based on the double ring electrode method described in JIS K 6271.

The resin foam of the present invention can be applied to a wide range of uses as described above. However, when the volume resistivity of the resin foam is 10 ⁸ Ω · cm or less, for example, it can be used in a clean room. When the volume resistivity of the resin foam is 10 ⁵ Ω · cm or less, the contacted electronic components are grounded to prevent malfunction due to electrostatic failure. It can be applied to a conductive buffer sealing material.

The repulsive load at the time of 50% compression of the resin foam is 5 N / cm ² or less, preferably 4 N / cm ² or less, more preferably 3 N / cm ² from the viewpoint of enabling application to a minute clearance. cm ² or less. In addition, the repulsive load at the time of 50% compression of a resin foam is measured according to the compression hardness measuring method described in JISK6767.

For example, if the repulsive load at the time of 50% compression of the resin foam is 4 N / cm ² or less, the followability to the uneven surface becomes very good, and particularly the uneven surface having a large uneven height (for example, 0.05 It can be suitably used for grounding applications of electronic components having a concavo-convex height of ˜0.20 mm.

In particular, the resin foam of the present invention has a compression resistivity defined below of 10 ⁸ Ω · cm or less from the viewpoint of exhibiting conductivity by following the step well in the step portion even when compressed. (More preferably 10 ⁶ Ω · cm or less).

The compression resistivity is determined by sandwiching the following resin foam between the upper electrode having the following steps and the lower electrode in the form in which the step surface of the upper electrode is in contact with the resin foam, and the resin foam from above. It is the volume resistivity when compressed in the thickness direction by 5% (compression rate 5%).
Resin foam: 25 mm long, 25 mm wide, 1 mm thick sheet-like resin foam Upper electrode having steps: 25 mm long, 25 mm wide, 25 mm long, 7.5 mm wide, 0. It is obtained by sticking a 1 mm PET tape to both ends of the electrode, and has a recess of 25 mm in length, 10 mm in width, and 0.1 mm in height on the side in contact with the resin foam.
Lower electrode: An electrode having a smooth surface of 25 mm long and 25 mm wide. FIG. 4 shows a schematic cross-sectional view of an example of an upper electrode having a step.

In the resin foam of the present invention, it is possible to suitably apply to a wide range of applications such as a conductive material, shock absorbing material, buffer seal material, conductive buffer seal material, dustproof material, conductive dustproof material, It is preferable to have a volume resistivity of 10 ¹⁰ Ω · cm or less and a surface resistivity of 10 ¹⁰ Ω / □ or less (preferably 10 ⁸ Ω / □ or less, more preferably 10 ⁵ Ω / □ or less).

For example, in the resin foam of the present invention, when the surface resistivity of the resin foam is 10 ⁸ Ω / □ or less, the resin foam is more preferably applied to an antistatic buffer seal material that can be used in a clean room. Can do. Further, when the surface resistivity of the resin foam is 10 ⁵ Ω / □ or less, it can be more suitably applied to a conductive buffer sealing material or the like that performs grounding of the contacted electronic component and prevents malfunction due to static electricity failure. .

In the resin foam of the present invention, the apparent density is preferably 0.15 g / cm ³ or less, more preferably 0.10 g / cm ³ or less, and even more preferably 0.000 from the point of increasing flexibility. 0.7 g / cm ³ or less. On the other hand, the apparent density is preferably 0.01 g / cm ³ or more, more preferably 0.02 g / cm ³ or more, from the viewpoint of ensuring excellent conductivity.

  In the resin foam of the present invention, the expansion ratio is preferably 9 times or more (for example, 9 times to 50 times), more preferably 15 times or more (for example, 15 times to 30 times). If the expansion ratio is less than 9 times, sufficient flexibility and impact absorption may not be obtained in the resin foam, whereas if the expansion ratio exceeds 50 times, the strength may be significantly reduced.

The expansion ratio of the resin foam is calculated from the following formula.
Foaming ratio (times) = (density before foaming) / (density after foaming)
The density before foaming is, for example, the density of an unfoamed molded product or a resin before foaming when a resin foam is formed by impregnating a molten resin with an inert gas after melting the resin composition. Corresponds to the density of the composition. Further, the density after foaming corresponds to the apparent density of the resin foam.

In the resin foam of the present invention, the average cell diameter (average cell diameter) is preferably 250 μm or less from the viewpoint of enabling thin layer processing and improving applicability to minute clearances, and improving dust resistance. Preferably it is 200 micrometers or less, More preferably, it is 100 micrometers or less, More preferably, it is 80 micrometers or less. On the other hand, the average cell diameter is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more from the viewpoint of obtaining excellent impact absorbability (cushioning property).

  In the resin foam of the present invention, the average cell diameter is preferably 250 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less, from the viewpoint of particularly improving dust resistance.

  In the resin foam of the present invention, the thickness is preferably 2.0 mm or less, more preferably 1.0 mm or less from the viewpoint of facilitating thin layer processing and improving operability to minute clearances. Yes, even more preferably 0.5 mm or less. In addition, the thickness of the resin foam is usually 0.2 mm or more, preferably 0.3 mm or more.

  In the resin foam of the present invention, the cell structure is a closed cell structure or a semi-continuous semi-closed cell structure (a closed cell structure and a semi-continuous semi-closed cell structure) from the viewpoint of forming a conductive path (conductive network) and dustproof. And the ratio is not particularly limited). In particular, a cell structure in which the closed cell structure part is 50% or more (in particular, 80% or more, particularly preferably 90% or more) in the resin foam is preferable.

  The volume resistivity and surface resistivity of the resin foam can be controlled by selecting a resin and adjusting the type and amount of the conductive substance.

  In the resin foam of the present invention, the repulsive load, the apparent density, the expansion ratio, the average cell diameter, and the cell structure at the time of 50% compression of the resin foam are the type of resin, the type of foaming agent, the conductive material, and others. Depending on the type of additive, etc., conditions for foam molding, for example, operating conditions such as temperature, pressure, time, amount of gas to be mixed in the gas impregnation process, operations such as decompression speed, temperature, pressure in the decompression process, etc. It can be adjusted by appropriately selecting and setting conditions, heating temperature after decompression, and the like.

For example, it contains a thermoplastic resin and a carbon-based filler, which will be described later, the BET specific surface area of the carbon-based filler is 500 m ² / g, and the added amount of the carbon-based filler is 3 to 20 weights with respect to 100 parts by weight of the thermoplastic resin. Part of the resin composition includes a thermoplastic resin and a carbon-based filler, the BET specific surface area of the carbon-based filler is 500 m ² / g, and the amount of carbon-based filler added is 100 parts by weight of the thermoplastic resin. To obtain a resin foam having a volume resistivity of 10 ¹⁰ Ω · cm or less and a repulsive load at 50% compression of 5 N / cm ² or less. Can do. Furthermore, it is a resin foam in which the addition amount of the carbon-based filler is 3 to 20 parts by weight with respect to 100 parts by weight of the thermoplastic resin, the volume resistivity is 10 ¹⁰ Ω · cm or less, and at 50% compression It is possible to obtain a resin foam in which the repulsive load is 5 N / cm ² or less and the surface resistivity, foaming magnification, apparent density, compression resistivity, average cell diameter and the like are controlled. For example, it contains a thermoplastic resin and a carbon-based filler, the BET specific surface area of the carbon-based filler is 500 m ² / g, and the added amount of the carbon-based filler is 3 to 20 parts by weight with respect to 100 parts by weight of the thermoplastic resin. The resin foam has a volume resistivity of 10 ¹⁰ Ω · cm or less, a repulsive load at 50% compression of 5 N / cm ² or less, an average cell diameter of 10 to 250 μm, and an apparent density of Examples thereof include a resin foam of 0.01 to 0.15 g / cm ³ .

  The resin foam of the present invention has both flexibility and conductivity, and is highly foamed and lightweight. Furthermore, it also has a follow-up capability for minute clearances. In particular, even if the foam is compressed, it has both flexibility and conductivity. For example, even when compressed by 5% in the thickness direction, it can follow the step well and exhibits a low volume resistivity.

  If the resin foam of the present invention has a fine cell structure, it also has shape processability. Furthermore, the dust resistance can be particularly improved by adjusting the average cell diameter.

  Since the resin foam of the present invention has the above properties, it can be suitably used as a conductive material, an impact absorbing material, a buffer seal material, a conductive buffer seal material, a dustproof material, a conductive dustproof material, and the like.

  Since the resin foam of the present invention has the above-mentioned characteristics and can fill a minute clearance between high-density parts, it can be used for various members or parts, electronic parts, electronic devices, and the like. It is particularly useful for downsizing and thinning. For example, it can be suitably used for liquid crystal display devices such as liquid crystal displays, electroluminescence displays, and plasma displays, and mobile communication devices such as mobile phones and portable information terminals.

(Resin composition)
The resin composition contains at least a resin and a conductive substance, and is a composition that forms a resin foam.

  In the present invention, the resin that is the material of the resin foam (foam) is not particularly limited as long as it is a polymer exhibiting thermoplasticity (thermoplastic polymer) and can be impregnated with a high-pressure gas. Examples of such thermoplastic polymers include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, a copolymer of ethylene and propylene, ethylene or propylene and other α-olefins. Olefin-based copolymers such as copolymers of ethylene and other ethylenically unsaturated monomers (for example, vinyl acetate, acrylic acid, acrylic ester, methacrylic acid, methacrylic ester, vinyl alcohol, etc.) Polystyrene such as polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS resin); polyamide such as 6-nylon, 66-nylon, 12-nylon; polyamideimide; polyurethane; polyimide; polyetherimide; Methyl methacrylate Which acrylic resins, polyvinyl chloride, polyvinyl fluoride; alkenyl aromatic resin; polyacetal; polycarbonate such as bisphenol-A based polycarbonate, polyethylene terephthalate, polyesters such as polybutylene terephthalate and poly (phenylene sulfide) and the like.

  The thermoplastic polymer also includes a thermoplastic elastomer that exhibits properties as a rubber at room temperature and exhibits thermoplasticity at a high temperature. Examples of such thermoplastic elastomers include olefin elastomers such as ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, polyisobutylene, and chlorinated polyethylene; Styrenic elastomers such as butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-isoprene-butadiene-styrene copolymers, and hydrogenated polymers thereof; thermoplastic polyester elastomers; thermoplastic polyurethane elastomers A thermoplastic acrylic elastomer and the like. These thermoplastic elastomers, for example, have a glass transition temperature of room temperature or lower (for example, 20 ° C. or lower), so that they are remarkably excellent in flexibility and shape followability when formed into a resin foam.

  A thermoplastic polymer can be used individually or in mixture of 2 or more types. Moreover, any of thermoplastic elastomers, thermoplastic polymers other than thermoplastic elastomers, and mixtures of thermoplastic elastomers and thermoplastic polymers other than thermoplastic elastomers can be used as the foam material.

  Examples of the mixture of the thermoplastic elastomer and a thermoplastic polymer other than the thermoplastic elastomer include a mixture of an olefin elastomer such as an ethylene-propylene copolymer and an olefin polymer such as polypropylene. When a mixture of a thermoplastic elastomer and a thermoplastic polymer other than the thermoplastic elastomer is used, the mixing ratio is, for example, the former / the latter = 1/99 to 99/1 (preferably about 10/90 to 90/10, More preferably, it is about 20/80 to 80/20).

  The conductive substance is included as an essential additive in the resin composition. For this reason, in the resin foam of this invention, formation of a conductive path, adjustment of electroconductivity, etc. are performed by forming with the resin composition to which the electroconductive substance was added. In addition, an electroconductive substance can be used individually or in combination of 2 or more types.

The conductive substance is not particularly limited as long as a conductive path is formed in the resin foam and the volume resistivity of the resin foam is 10 ¹⁰ Ω · cm or less. In the present invention, the resin composition preferably contains a carbon-based filler as an essential component as a conductive substance from the viewpoint of ease of forming a conductive path, ease of adjusting conductivity, stability of characteristics, and the like. .

  In addition, in this invention, fillers other than carbon type fillers, such as a metal type filler and the following other filler, may be contained as arbitrary electroconductive substances.

  Examples of such metal fillers include pure metal fillers such as copper, silver, gold, iron, platinum, nickel, and aluminum; alloy fillers such as stainless steel and brass; aluminum oxide, titanium oxide, zinc oxide, silver oxide, Examples thereof include metal oxide fillers such as magnesium oxide, calcium oxide, barium oxide, strontium oxide, silicon oxide, and zirconium oxide. Examples of other fillers include carbonates such as calcium carbonate and magnesium carbonate, sulfates such as barium sulfate, hydroxides such as aluminum hydroxide and magnesium hydroxide, silicic acid and salts thereof, clay, talc, and mica. (Mica), bentonite, silica, aluminum silicate, basalt fiber and the like.

  In the present invention, in the resin composition, when the conductive material contains a carbon-based filler as an essential component and a filler other than the carbon-based filler as an optional component, the carbon-based filler is the total weight of the conductive material. It is important to occupy 80% by weight or more (preferably 90% by weight or more).

  Examples of the carbon-based filler include carbon fiber, carbon black, graphite (graphite), carbon nanotube, fullerene, activated carbon and the like.

Among the carbon-based fillers, so-called conductive carbon black is preferable from the viewpoint of easy formation of a conductive path in a resin foam, ease of adjusting conductivity, characteristic stability, and the like.
Examples of the conductive carbon black include acetylene black, ketjen black, furnace black, channel black, thermal black, and carbon nanotube. Among these, ketjen black is preferable as the conductive carbon black.

As a structure of the conductive material, desired conductivity can be obtained with a small amount of addition, a decrease in the performance of the resin composition (for example, a decrease in fluidity) can be suppressed when the added weight of the conductive material is small, and a surface area. Is large, it is preferable that the conductive material has a structure with a BET specific surface area of 500 m ² / g or more (preferably 1000 m ² / g or more).

  The shape of the conductive substance is not particularly limited, and examples thereof include a powdery indefinite shape, a spherical shape, a rod shape, a short fiber shape, a plate shape, and a cylindrical shape (tube shape). In addition, when the shape of the conductive substance is a cylindrical shape (tube shape) or the like, a large specific surface area is easily obtained.

  The conductive material may have a hollow structure. When it has a hollow structure, it is easy to obtain a large BET specific surface area.

  In the present invention, a conductive material having a hollow structure is preferably used as compared with a conductive material having a solid structure. In the formation of the conductive path in the resin foam, not the weight of the conductive material but the surface area of the conductive material has a great influence. The conductive material having a hollow structure is a conductive material having a solid structure. This is because the surface area per weight can be increased. Moreover, since the addition weight of the electroconductive substance per volume can be suppressed, the performance fall of a resin composition can be suppressed.

  The surface shape of the conductive material is not particularly limited, and may be smooth or may have irregularities. A large specific surface area is easily obtained when the surface shape of the conductive material is an uneven shape or a porous shape.

  The addition amount of the conductive substance is not particularly limited, but is preferably 3 to 20 parts by weight, and preferably 5 to 10 parts by weight with respect to 100 parts by weight of the resin. If the amount is less than 5 parts by weight, sufficient conductive performance may not be obtained. On the other hand, if it exceeds 20 parts by weight, the fluidity of the resin composition may be lowered, and a highly foamed foam may not be obtained.

  In the present invention, an additive may be added as necessary in addition to the conductive substance. The kind of additive is not specifically limited, Various additives normally used for foam molding can be used. Examples of such additives include cell nucleating agents, crystal nucleating agents, plasticizers, lubricants, colorants (pigments, dyes, etc.), ultraviolet absorbers, antioxidants, anti-aging agents, and the above conductive substances. Examples include fillers, reinforcing agents, flame retardants, antistatic agents, surfactants, vulcanizing agents, and surface treatment agents. The addition amount of the additive can be appropriately selected within a range that does not impair the formation of bubbles and the like, and the addition amount used for normal resin foaming and molding can be adopted. In addition, an additive can be used individually or in combination of 2 or more types.

  The lubricant improves the fluidity of the resin and suppresses the thermal degradation of the resin. The lubricant used in the present invention is not particularly limited as long as it has an effect on improving the fluidity of the resin. For example, hydrocarbon lubricants such as liquid paraffin, paraffin wax, microwax and polyethylene wax; stearic acid Fatty acid lubricants such as behenic acid and 12-hydroxystearic acid; and ester lubricants such as butyl stearate, monoglyceride stearate, pentaerythritol tetrastearate, hydrogenated castor oil, stearyl stearate, and the like. Such lubricants can be used alone or in combination of two or more.

  The addition amount of the lubricant is, for example, 0.5 to 10 parts by weight (preferably 0.8 to 8 parts by weight, more preferably 1 to 6 parts by weight) with respect to 100 parts by weight of the resin. When the addition amount exceeds 10 parts by weight, the fluidity becomes too high and the expansion ratio may be lowered. On the other hand, if it is less than 0.5 parts by weight, the fluidity cannot be improved, the stretchability at the time of foaming is lowered, and the foaming ratio may be lowered.

  The anti-shrinkage agent has a function of effectively suppressing permeation of the foaming agent gas by forming a molecular film on the surface of the foam film of the foam. The shrinkage preventing agent used in the present invention is not particularly limited as long as it has an effect of suppressing the permeation of the blowing agent gas. For example, fatty acid metal salts (for example, stearic acid, behenic acid, 12-hydroxystearic acid) Fatty acid such as aluminum, calcium, magnesium, lithium, barium, zinc, lead salt, etc.); fatty acid amide [fatty acid amide (monoamide or bisamide) having about 12 to 38 carbon atoms (preferably about 12 to 22 carbon atoms) However, bisamide is preferably used to obtain a fine cell structure.), For example, stearic acid amide, oleic acid amide, erucic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, Lauric acid bisamide, etc.]. Such anti-shrinkage agents can be used alone or in combination of two or more.

  The addition amount of the shrinkage inhibitor is, for example, 0.5 to 10 parts by weight (preferably 0.7 to 8 parts by weight, more preferably 1 to 6 parts by weight) with respect to 100 parts by weight of the resin. If the addition amount exceeds 10 parts by weight, gas efficiency is lowered in the cell growth process, so that a cell having a small cell diameter can be obtained, but there are also many unfoamed portions, which may reduce the foaming ratio. On the other hand, if the amount is less than 0.5 part by weight, the coating film is not sufficiently formed, and gas escape occurs at the time of foaming, causing shrinkage and reducing the foaming ratio.

  In addition, you may use an additive in combination with the said lubricant and the said shrinkage | contraction inhibitor, for example. For example, a lubricant such as stearic acid monoglyceride and a shrinkage preventing agent such as erucic acid amide or lauric acid bisamide may be used in combination.

  The resin composition can be obtained by a known / conventional method. For example, the resin composition can be obtained by adding and kneading a conductive material and, if necessary, an additive to a resin that is a raw material of the foam. In addition, in kneading | mixing, you may heat.

Specific embodiments of the resin composition used for forming a resin foam satisfying a volume resistivity of 10 ¹⁰ Ω · cm or less and a repulsive load at 50% compression of 5 N / cm ² or less include, for example, heat A resin composition comprising a plastic resin and a carbon-based filler, wherein the carbon-based filler has a BET specific surface area of 500 m ² / g, and the added amount of the carbon-based filler is 3 to 20 parts by weight with respect to 100 parts by weight of the thermoplastic resin. Is mentioned.

(Manufacture of resin foam)
The resin foam of the present invention is formed from a resin composition containing at least a resin and a conductive substance. In the resin foam of the present invention, the method for producing the resin foam is not particularly limited, and examples thereof include commonly used methods such as a physical method and a chemical method. A general physical method is a method of forming bubbles by dispersing a low boiling point liquid (foaming agent) such as chlorofluorocarbons or hydrocarbons in a resin, and then heating to volatilize the foaming agent. Moreover, a general chemical method is a method in which bubbles are formed by a gas generated by thermal decomposition of a compound (foaming agent) added to a resin. However, general physical methods are concerned about flammability and toxicity of substances used as foaming agents, and environmental effects such as ozone layer destruction. Also, in general chemical methods, foaming gas residues remain in the foam, so that contamination by corrosive gas and impurities in the gas is a problem, especially in electronic equipment applications where low pollution requirements are high. Become. Moreover, in any of these physical methods and chemical methods, it is difficult to form a fine bubble structure, and it is extremely difficult to form fine bubbles of 300 μm or less.

  For this reason, in the present invention, a method using a high-pressure inert gas as the foaming agent is preferable because a foam having a small cell diameter and a high cell density can be easily obtained.

  Specifically, as a method for forming the resin foam of the present invention from a resin composition by a method using a high-pressure inert gas as a foaming agent, for example, a gas for impregnating a resin with an inert gas under high pressure is used. Examples include an impregnation step, a pressure reduction step in which the pressure is reduced after the step to foam the resin, and a heating method in which bubbles are grown by heating as necessary. In this case, after molding the resin composition in advance to obtain an unfoamed molded product, the unfoamed molded product may be impregnated with an inert gas, or after melting the resin composition, After impregnating the inert gas under pressure, it may be subjected to molding during decompression. These steps may be performed by either a batch method or a continuous method.

  The inert gas used in the present invention is not particularly limited as long as it is inert with respect to the resin and can be impregnated, and examples thereof include carbon dioxide, nitrogen gas, and air. These gases may be mixed and used. Among these, carbon dioxide having a large amount of impregnation into the resin used as the material of the foam and having a high impregnation rate is preferable. Carbon dioxide is also preferred from the viewpoint of obtaining a clean resin foam with few impurities.

  In addition, the inert gas when impregnating the resin is preferably in a supercritical state. In the supercritical state, the solubility of the gas in the resin is increased and high concentration can be mixed. In addition, when the pressure drops rapidly after impregnation, since the concentration is high as described above, the generation of bubble nuclei is increased, and the density of bubbles formed by the growth of the bubble nuclei is the same as the porosity. Since it becomes large, fine bubbles can be obtained. Carbon dioxide has a critical temperature of 31 ° C. and a critical pressure of 7.4 MPa.

  According to the batch method, for example, a resin foam can be formed as follows. That is, first, an unfoamed molded product (such as a resin sheet for foam molding) is formed by extruding the resin composition using an extruder such as a single screw extruder or a twin screw extruder. Alternatively, using a kneader equipped with rollers, cams, kneaders, and Banbury type blades, the resin composition is uniformly kneaded, and this is press-molded using a hot plate press, and then unfoamed. A product (such as a resin sheet for forming a foam). Then, the obtained unfoamed molded product is put in a pressure vessel, a high-pressure inert gas is introduced, and the inert gas is impregnated in the unfoamed molded product. In this case, the shape of the unfoamed molded product is not particularly limited, and may be any of a roll shape, a plate shape, and the like. The introduction of the high-pressure inert gas may be performed continuously or discontinuously. When impregnated with a sufficiently high-pressure inert gas, the pressure is released (usually up to atmospheric pressure) to generate bubble nuclei in the resin. Bubble nuclei may be grown at room temperature as they are, or may be grown by heating as necessary. As a heating method, a known or conventional method such as a water bath, an oil bath, a hot roll, a hot air oven, a far infrared ray, a near infrared ray, or a microwave can be adopted. After the bubbles are grown in this way, the shape is fixed rapidly by cooling with cold water or the like.

  On the other hand, according to the continuous method, for example, a resin foam can be formed as follows. That is, a high-pressure inert gas is injected while kneading the resin composition using an extruder such as a single-screw extruder or a twin-screw extruder, and the resin is sufficiently impregnated in the resin, and then extruded and pressurized. Is released (usually up to atmospheric pressure), foaming and molding are performed simultaneously, and in some cases, the bubbles are grown by heating. After the bubbles are grown, the shape is fixed rapidly by cooling with cold water or the like.

  The pressure in the gas impregnation step is, for example, 6 MPa or more (for example, about 6 to 100 MPa), preferably 8 MPa or more (for example, about 8 to 100 MPa). When the pressure is lower than 6 MPa, the bubble growth at the time of foaming is remarkable, the bubble diameter becomes too large, a small average cell diameter (average bubble diameter) in the above range cannot be obtained, and the dustproof effect is reduced. This is because, when the pressure is low, the amount of gas impregnation is relatively small compared to when the pressure is high, and the number of bubble nuclei formed is reduced due to a decrease in the bubble nucleus formation rate. This is because the bubble diameter becomes extremely large. Further, in the pressure region lower than 6 MPa, the bubble diameter and the bubble density change greatly only by slightly changing the impregnation pressure, so that it is difficult to control the bubble diameter and the bubble density.

  The temperature in the gas impregnation step varies depending on the type of inert gas and resin to be used and can be selected in a wide range. However, considering operability and the like, it is, for example, about 10 to 350 ° C. For example, the impregnation temperature when impregnating an inert gas into an unfoamed molded product such as a sheet is about 10 to 250 ° C., preferably about 10 to 200 ° C., more preferably about 40 to 200 ° C. in a batch system. . Further, the impregnation temperature in the case where the molten resin composition impregnated with gas is extruded and foaming and molding are simultaneously performed is generally about 60 to 350 ° C. in a continuous type. When carbon dioxide is used as the inert gas, the temperature during impregnation is preferably 32 ° C. or higher, particularly 40 ° C. or higher in order to maintain a supercritical state.

  The mixing amount of the inert gas (gas as a foaming agent) is not particularly limited, but it is a thermoplastic resin composition from the viewpoint of foamability and a cell structure having a small average cell diameter such as the average cell diameter. It is preferably 1 to 15% by weight, more preferably 2 to 12% by weight, still more preferably 3 to 10% by weight, based on the total amount of the resin.

  In the decompression step, the decompression rate is not particularly limited, but is preferably about 5 to 300 MPa / second in order to obtain uniform fine bubbles. Moreover, the heating temperature in the said heating process is about 40-250 degreeC, for example, Preferably it is about 60-250 degreeC.

Specific embodiments of the production method used for forming a resin foam satisfying a volume resistivity of 10 ¹⁰ Ω · cm or less and a repulsive load at 50% compression of 5 N / cm ² or less include, for example, Embodiment 1 As the method, the resin composition is impregnated with a high-pressure inert gas and then formed through a step of reducing the pressure. Moreover, as aspect 2, the method of forming through the process of depressurizing, after impregnating the non-foamed molding which consists of the said resin composition with a high pressure inert gas is mentioned.

More specific embodiments include, for example, a thermoplastic resin and a carbon-based filler, the BET specific surface area of the carbon-based filler is 500 m ² / g, and the added amount of the carbon-based filler is 100 parts by weight of the thermoplastic resin. 3 to 20 parts by weight of resin composition impregnated with a high-pressure inert gas, followed by a pressure reduction process, a thermoplastic resin and a carbon-based filler, and a BET ratio of the carbon-based filler A non-foamed molded article made of a resin composition having a surface area of 500 m ² / g and a carbon filler content of 3 to 20 parts by weight with respect to 100 parts by weight of a thermoplastic resin is impregnated with a high-pressure inert gas. The method of forming through the process of decompressing after making it reduce, etc. are mentioned.

(Conductive foam member)
The conductive foam member is composed of at least the resin foam. Specifically, the conductive foam member may be composed only of a resin foam, or another layer or a substrate (particularly an adhesive layer or the like) is provided on one or both sides of the resin foam. It may be a configuration.

  When the conductive foam member has a configuration in which an adhesive layer is provided on one or both surfaces of the resin foam, a member or component such as an optical member can be fixed or temporarily fixed to the adherend.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and examples thereof include acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives (natural rubber-based pressure-sensitive adhesives, synthetic rubber-based pressure-sensitive adhesives), silicone-based pressure-sensitive adhesives, and polyester-based pressure-sensitive adhesives. Known pressure-sensitive adhesives such as adhesives, urethane-based pressure-sensitive adhesives, polyamide-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, vinyl alkyl ether-based pressure-sensitive adhesives, and fluorine-based pressure-sensitive adhesives can be appropriately selected and used. An adhesive can be used individually or in combination of 2 or more types. The pressure-sensitive adhesive may be any type of pressure-sensitive adhesive such as an emulsion-based pressure-sensitive adhesive, a hot-melt pressure-sensitive adhesive, a solvent-based pressure-sensitive adhesive, an oligomer-based pressure-sensitive adhesive, or a solid-based pressure-sensitive adhesive. Among these, an acrylic pressure-sensitive adhesive is suitable as the pressure-sensitive adhesive from the viewpoint of preventing contamination of the adherend.

  The pressure-sensitive adhesive layer can be formed by using a known or conventional forming method. For example, a method of applying a pressure-sensitive adhesive on a predetermined site or surface (coating method), a pressure-sensitive adhesive film on a release film such as a release liner, etc. Examples thereof include a method (transfer method) of applying an agent to form an adhesive layer and then transferring the adhesive layer onto a predetermined site or surface. In forming the pressure-sensitive adhesive layer, a known or conventional coating method (such as a casting method, a roll coater method, a reverse coater method, a doctor blade method) can be appropriately used.

  The thickness of the adhesive layer is usually about 2 to 100 μm (preferably 10 to 100 μm). The thinner the adhesive layer, the higher the effect of preventing the adhesion of dust and dirt at the end, so the thinner it is preferable. In addition, the adhesion layer may have any form of a single layer or a laminated body.

  Moreover, the adhesion layer may be formed on the foam through another layer (lower layer). Examples of such a lower layer include a base material layer (in particular, a film layer and a nonwoven fabric), other adhesive layers, an intermediate layer, an undercoat layer, and the like.

  Furthermore, when the adhesive layer is formed only on one side (one side) of the foam, another layer may be formed on the other side of the foam, for example, other types of adhesives. Examples thereof include a layer and a base material layer.

  The conductive foam member or the resin foam constituting the conductive foam member may be processed so as to have a desired shape or thickness. For example, a conductive foam member having a desired thickness can be obtained by slicing the conductive foam member. In addition, various shapes may be processed according to the device or equipment used.

  The conductive foam member can be suitably used as, for example, a seal material, a conductive material, an impact absorbing material, a buffer seal material, a conductive buffer seal material, a dustproof material, a conductive dustproof material, and the like.

  The conductive foam member is preferably used particularly in an electronic device or the like. This is because the resin foam constituting the conductive foam member is excellent in flexibility, and further, an inert gas such as carbon dioxide is used as a foaming agent during production. This is because there is no residue and it is clean.

  The conductive foam member is used when, for example, various members or parts (for example, optical members) are attached (attached) to a predetermined site. In particular, it is preferably used even when a small member or component (for example, a small optical member) is mounted on a thin product.

  As an optical member attached (attached) using a conductive foam member, for example, an image display member attached to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display (particularly, a small image display member) ), Or a camera or lens (particularly, a small camera or lens) mounted on a mobile communication device such as a so-called “mobile phone” or “portable information terminal”.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
Polypropylene [melt flow rate (MFR): 0.35 g / 10 min]: 50 parts by weight, polyolefin elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 50 parts by weight, magnesium hydroxide : 10 parts by weight, carbon (trade name “Ketjen Black EC-600JD” manufactured by Ketjen Black International Co., Ltd., hollow shell structure, BET specific surface area: 1270 m ² / g): 10 parts by weight, stearic acid monoglyceride: 1 part by weight The part was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by Japan Steel Works (JSW), then extruded into a strand shape, water-cooled and formed into a pellet shape. The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected under an atmosphere of 220 ° C. at a pressure of 13 (12 after injection) MPa. Carbon dioxide gas was injected at a ratio of 6.0% by weight with respect to the total amount of the polymer. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from a die to obtain a foam.

(Example 2)
Polypropylene [melt flow rate (MFR): 0.35 g / 10 min]: 50 parts by weight, polyolefin elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 50 parts by weight, magnesium hydroxide : 10 parts by weight, carbon (trade name “Ketjen Black EC-600JD” manufactured by Ketjen Black International Co., Ltd., hollow shell structure, BET specific surface area: 1270 m ² / g): 10 parts by weight, stearic acid monoglyceride: 1 part by weight The part was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by Japan Steel Works (JSW), then extruded into a strand shape, water-cooled and formed into a pellet shape. The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected under an atmosphere of 220 ° C. at a pressure of 13 (12 after injection) MPa. Carbon dioxide gas was injected at a ratio of 5.0% by weight with respect to the total amount of the polymer. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from a die to obtain a foam.

(Example 3)
Polypropylene [melt flow rate (MFR): 0.35 g / 10 min]: 70 parts by weight, polyolefin-based elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 30 parts by weight, magnesium hydroxide : 10 parts by weight, carbon (trade name “Ketjen Black EC-600JD” manufactured by Ketjen Black International Co., Ltd., hollow shell structure, BET specific surface area: 1270 m ² / g): 10 parts by weight, stearic acid monoglyceride: 1 part by weight The part was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by Japan Steel Works (JSW), then extruded into a strand shape, water-cooled and formed into a pellet shape. The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected under an atmosphere of 220 ° C. at a pressure of 13 (12 after injection) MPa. Carbon dioxide gas was injected at a ratio of 5.0% by weight with respect to the total amount of the polymer. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from a die to obtain a foam.

Example 4
Polypropylene [melt flow rate (MFR): 0.35 g / 10 min]: 70 parts by weight, polyolefin-based elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 30 parts by weight, magnesium hydroxide : 10 parts by weight, carbon (trade name “Ketjen Black EC-600JD” manufactured by Ketjen Black International Co., Ltd., hollow shell structure, BET specific surface area: 1270 m ² / g): 10 parts by weight, stearic acid monoglyceride: 1 part by weight The part was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by Japan Steel Works (JSW), then extruded into a strand shape, water-cooled and formed into a pellet shape. The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected under an atmosphere of 220 ° C. at a pressure of 13 (12 after injection) MPa. Carbon dioxide gas was injected at a ratio of 4.0% by weight with respect to the total amount of the polymer. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from a die to obtain a foam.

(Example 5)
Polypropylene [melt flow rate (MFR): 0.35 g / 10 min]: 50 parts by weight, polyolefin elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 50 parts by weight, magnesium hydroxide : 10 parts by weight, carbon (trade name “Ketjen Black EC-600JD” manufactured by Ketjen Black International Co., Ltd., hollow shell structure, BET specific surface area: 1270 m ² / g): 10 parts by weight, stearic acid monoglyceride: 1 part by weight The part was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by Japan Steel Works (JSW), then extruded into a strand shape, water-cooled and formed into a pellet shape. The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected under an atmosphere of 220 ° C. at a pressure of 13 (12 after injection) MPa. Carbon dioxide gas was injected at a ratio of 3.5% by weight with respect to the total amount of the polymer. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from a die to obtain a foam.

(Comparative Example 1)
Polypropylene [melt flow rate (MFR): 0.35 g / 10 min]: 50 parts by weight, polyolefin-based elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 50 parts by weight, magnesium hydroxide : 10 parts by weight, carbon (trade name “Asahi # 35” manufactured by Asahi Carbon Co., Ltd., BET specific surface area: 23 m ² / g, solid structure): 10 parts by weight, stearic acid monoglyceride: 1 part by weight, Nippon Steel Works After being kneaded at a temperature of 200 ° C. by a twin screw kneader manufactured by (JSW), it was extruded into a strand shape, formed into a pellet shape after water cooling. The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected under an atmosphere of 220 ° C. at a pressure of 13 (12 after injection) MPa. Carbon dioxide gas was injected at a ratio of 6.0% by weight with respect to the total amount of the polymer. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from a die to obtain a foam.

(Comparative Example 2)
Polypropylene [melt flow rate (MFR): 0.35 g / 10 min]: 50 parts by weight, polyolefin elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 50 parts by weight, magnesium hydroxide : 10 parts by weight, carbon (trade name “Ketjen Black EC-600JD” manufactured by Ketjen Black International Co., Ltd., hollow shell structure, BET specific surface area: 1270 m ² / g): 25 parts by weight, stearic acid monoglyceride: 1 part by weight The part was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by Japan Steel Works (JSW), then extruded into a strand shape, water-cooled and formed into a pellet shape. The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected under an atmosphere of 220 ° C. at a pressure of 13 (12 after injection) MPa. Carbon dioxide gas was injected at a ratio of 6.0% by weight with respect to the total amount of the polymer. The carbon dioxide gas was sufficiently saturated and then cooled to a temperature suitable for foaming. However, the fluidity of the resin composition was low, and a foam could not be obtained.

(Comparative Example 3)
A commercially available conductive foam in which an antistatic agent was blended with a mixed resin of low density polyethylene resin and ethylene vinyl acetate resin was used.

(Evaluation)
For foams according to examples and comparative examples, volume resistivity, surface resistivity, repulsive load at 50% compression (50% compression load), apparent density, cell diameter, foaming magnification, clearance follow-up property, dustproof index And the compression resistivity was measured or evaluated. The results are shown in Table 1.

(Volume resistivity and surface resistivity)
Volume resistivity and surface resistivity were measured according to the double ring electrode method described in JIS K 6271. The device name “Digital Multimeter VOAC 7520” (manufactured by Iwadori Measurement Co., Ltd.) was used for measuring the resistance value.

(Repulsive load at 50% compression (50% compression load))
It measured according to the compression hardness measuring method described in JIS K 6767.

(Apparent density)
The foam is punched with a 40 mm / 40 mm punching blade mold, and the dimensions of the punched sample are measured. Further, the thickness is measured with a 1/100 dial gauge having a measurement terminal diameter (φ) of 20 mm. The volume of the foam was calculated from these values. Next, the weight of the foam is measured with an upper pan balance having a minimum scale of 0.01 g or more. From these values, the apparent density (g / cm ³ ) of the foam was calculated.

(Average cell diameter)
A digital microscope (trade name “VH-8000” manufactured by Keyence Corporation) is used to capture an enlarged image of the foam bubble, and image analysis is performed using image analysis software (trade name “Win ROOF”, manufactured by Mitani Corporation). The average cell diameter (μm) was determined.

(Foaming ratio)
The density before foaming was measured and determined from the following formula.
Foaming ratio (times) = (density before foaming) / (density after foaming)
The density before foaming is the density of the pellets of Examples and Comparative Examples, and the density after foaming is the apparent density of the foams of Examples and Comparative Examples.

(Clearance tracking)
The foams (foams 13) of Examples and Comparative Examples are set in a jig (clearance followability evaluation jig 1) as shown in FIG. 1, and an acrylic plate (a 10 mm thick acrylic plate 11a) on the upper surface side is set. ) Was observed visually. Specifically, a spacer having a thickness of 0.1 mm (spacer 12 having a thickness of 0.1 mm) is installed on the left and right ends of an acrylic plate having a thickness of 20 mm (acrylic plate 11b having a thickness of 20 mm), and the spacer A foam (foam 13) is placed in the center between the two, and an acrylic plate with a thickness of 10 mm (acrylic plate 11a with a thickness of 10 mm) is placed on the top surface. The acrylic plate (acrylic plate 11a having a thickness of 10 mm) is compressed by applying a load (load a) from the side, and the presence or absence of deformation of the acrylic plate on the upper surface side (the acrylic plate 11a having a thickness of 10 mm) is visually observed. did. A case where no deformation was observed was evaluated as “good”, and a case where deformation was observed was evaluated as “bad”.
In addition, the thickness of the foam of the Example set to the jig | tool and the comparative example was 1 mm.

(Measurement method of dustproof index)
For the measurement of the dustproof index, the dustproof evaluation test apparatus shown in FIGS. 2 and 3 was used. 2 and 3, 2a is a schematic configuration of a dustproof evaluation test apparatus, 2b is a schematic configuration of a cross section of the dustproof evaluation test apparatus, 21 is a ceiling plate, 22 is a spacer, 23 is a double-sided tape (frame-shaped double-sided adhesive) Tape, product name “No. 5603”, manufactured by Nitto Denko Corporation, thickness: 30 μm), 24 is a foam (foam of Example and Comparative Example punched into a frame shape), and 25 is an evaluation box 26a is a through hole connected to the metering pump via a pipe joint, 26b is a through hole connected to the particle counter via the pipe joint, 26c is a through hole connected to the needle valve via the pipe joint, and 27 is an opening. (A square shape with a side length of 52 mm), 28 indicates a space portion. The dustproof evaluation test apparatus can form a substantially rectangular parallelepiped sealable space portion 28 by screwing the substantially square flat ceiling plate 21 and the evaluation box 25 to each other. The opening 27 is an opening of the space 28. Further, the ceiling plate 21 has a rectangular (trapezoidal) cut in plan view to be an opening.

  A rectangular flat spacer 22 larger than the opening 27 is attached to the lower surface of the ceiling plate 21 facing the opening 27 so as to face the entire surface of the opening 27. Then, a foam 24 having a window portion of almost the same size as the opening 27 is attached via a double-sided tape 23 at a position facing the opening 27 on the lower surface of the spacer 22. For this reason, by screwing the ceiling plate 21, the foam 24 is compressed in the thickness direction by the spacer 22 and the peripheral edge portion of the opening 27. The compression rate of the foam 24 is adjusted by adjusting the thickness of the spacer 22.

  Therefore, by screwing the ceiling plate 21 and the evaluation box 25, the space 28 in the evaluation box 25 is sealed by the foam 24, the double-sided tape 23, and the spacer 22.

  For the examples and comparative examples (thickness: 1 mm, width: 1 mm, length of one side of 54 mm, opening: square shape of one side having a length of 52 mm) punched into a frame shape, the dustproof evaluation The number of particles having a diameter of 0.5 μm or more that passed through was determined by a test apparatus.

Specifically, the examples and comparative examples in which the foams of the examples and comparative examples punched into the above-described frame shape were set in a dustproof evaluation test apparatus at a compression rate of 50% and were punched into the frame shape. A dustproof evaluation test apparatus set with a foam was placed in the dust box and sealed.
Next, using a dust supply device connected to the dust box body and a particle counter connected to the dust box body, the particle count value (number) of particles having a diameter of 0.5 μm or more in the sealed dust box body is around 1000000. Was controlled to be almost constant.
Next, with the needle valve of the through hole 26c closed, suction is performed from the through hole 26a with a metering pump at a suction speed of 0.5 L / min for 30 minutes, and after suction, the space portion of the dustproof evaluation test apparatus The number of particles having a diameter of 0.5 μm or more of 28 was measured with a particle counter to determine the number of particles that entered through the foam.
The number of particles was used as a dustproof index.

  The dustproof index is preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 10,000 or less, from the viewpoint of enhancing dustproofness.

(Compression resistivity) (Volume resistivity when a 1 mm thick resin foam is compressed 5% in the thickness direction with a jig having a height difference of 0.1 mm)
Prepare an electrode (length: 25 mm, width: 25 mm) connected to a data acquisition device (device name “Omniace II RA1200”, manufactured by NEC Avio Infrared Technology Co., Ltd.), and prepare PET tape (length: 25 mm, width: 7.5 mm, thickness: 0.2 mm) was affixed to both ends of the electrode to produce a step (step portion) (see FIG. 4). And the electrode which affixed PET tape was made into the upper electrode.
In addition, the schematic sectional drawing of the upper electrode which affixed PET tape is shown in FIG. In FIG. 4, 41 indicates an electrode, and 42 indicates a PET tape.
Separately, an electrode (vertical: 25 mm, width: 25 mm) connected to the above apparatus was prepared and used as a lower electrode. The lower electrode has a flat surface.
Next, the foams obtained in the examples and comparative examples were processed into a predetermined size (length: 25 mm, width: 25 mm, thickness: 1 mm sheet), and the processed foam was made conductive. Acrylic double-sided adhesive tape (trade name “Conductive copper foil double-sided tape No. 792”, manufactured by Teraoka Seisakusho Co., Ltd., adhesive: acrylic conductive adhesive, tape thickness: 0.09 mm, electric resistance: 0 .02Ω / cm ² ) to the lower electrode. After fixing, the upper electrode was allowed to stand on the foam so that the stepped surface was in contact with the foam.
Next, the volume resistivity was measured while compressing the foam from the top using an electromagnetic force micro tester (device name “MMT-250”, manufactured by Shimadzu Corporation).
And the volume resistivity at the time of compressing 5% in the thickness direction of a foam (compression rate 5%) was made into the compression resistivity.

Examples 1-5 followed the level | step-difference part even if it was a low compression rate of 5%, and showed the low volume resistivity. However, in Comparative Example 3, when the compression rate was 5%, it was impossible to follow the stepped portion, and the volume resistivity could not be measured.

  In Comparative Example 2, a foam could not be obtained.

DESCRIPTION OF SYMBOLS 1 Clearance follow-up evaluation jig | tool 11a 10-mm-thick acrylic board 11b 20-mm-thick acrylic board 12 0.1-mm-thick spacer 13 Foam a Load 2a Schematic structure of a dust-proof evaluation test apparatus 2b Dust-proof evaluation test apparatus Schematic configuration of the cross section 21 Ceiling plate 22 Spacer 23 Double-sided tape 24 Foam 25 Evaluation box 26a Through hole 26b Through hole 26c Through hole 27 Opening portion 28 Space portion 41 Electrode 42 PET tape

Claims (17)

A volume resistivity of 7.6 × 10 ⁵ Ω · cm or less, and Ri der repulsive load at 50% compression is 5N / cm ² or less, an apparent density be 0.01~0.15g / cm ³ A resin foam having an average cell diameter of 10 to 250 μm . The resin foam according to claim 1, wherein the resin foam has a surface resistivity of 10 ¹⁰ Ω · / □ or less.   The resin foam according to claim 1 or 2, wherein the foaming ratio of the resin foam is 9 times or more. The resin foam of any one of Claims 1-3 formed from the resin composition containing resin and an electroconductive substance. The resin foam according to claim 4, wherein the conductive substance is a carbon-based filler. The resin foam according to any one of claims 1 to 5, wherein the resin is a thermoplastic resin. Including thermoplastic resin and carbon filler, BET specific surface area of carbon filler is 500m ² / G or more, the addition amount of the carbon-based filler is 3 to 20 parts by weight with respect to 100 parts by weight of the thermoplastic resin, the average cell diameter is 10 to 250 μm, and the apparent density is 0.01 to 0.15 g. / Cm ^Three The resin foam according to any one of claims 1 to 6. The resin foam according to any one of claims 1 to 7, wherein the resin foam has a closed cell structure or a semi-continuous semi-closed cell structure. The resin foam according to any one of claims 1 to 8, which is formed through a step of depressurizing after impregnating a resin composition containing a resin and a conductive substance with a high-pressure inert gas. Including thermoplastic resin and carbon filler, BET specific surface area of carbon filler is 500m ² After impregnating a resin composition having a carbon filler content of 3 to 20 parts by weight with respect to 100 parts by weight of the thermoplastic resin with a high-pressure inert gas and then reducing the pressure, The resin foam according to any one of claims 1 to 9, which is formed. The resin foam according to claim 9 or 10, wherein the inert gas is carbon dioxide. The resin foam according to any one of claims 9 to 11, wherein the inert gas is in a supercritical state. The resin foam according to any one of claims 1 to 12, which is used as a buffer sealing material. The electroconductive foaming member which has the adhesion layer in the single side | surface or both surfaces of the resin foam of any one of Claims 1-13. The conductive foam member according to claim 14, wherein the adhesive layer is formed on the foam via a film layer. The conductive foam member according to claim 14 or 15, wherein the adhesive layer is formed of an acrylic adhesive. The conductive foam member according to any one of claims 14 to 16, which is used as a buffer seal material.

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